It is well known that turbo-supercharged diesel engines cannot operate efficiently at high power level unless its charging air pressure defining air supply is properly matched with the rate of fuel supply, and that when diesel engine crankshaft speed is caused to change by sudden application of load, or when the speed setting of the governor of the diesel engine is abruptly changed, i.e., when the unbalance of the rates of fuel supply and of air supply occurs.
In such cases the turbo-supercharged diesel engine combusts inefficiently the fuel supplied thereto until the turbo-supercharger causes the air pressure to become increased to an amount corresponding to a new load, i.e. to a new rate of fuel supply.
The disturbance of the matched rate of fuel supply and air supply, i.e., the unbalance of fuel and air leads to an excessive smoke of the engine exhaust, to an increased yield of toxic components in the exhaust gases, to a significant deposit of soot in the combustion chamber and exhaust passage, decreasing an efficiency of the diesel engine.
For preventing such unbalance of air and fuel supply during the periods of unsteady operating conditions diesel engines are equipped with load control devices.
In the heretofore known load control devices adjusting the load on an engine as a function of charging air pressure and rate of fuel supply, the control of the load fitted to the charging air, is accomplished through a means governing the load in accordance with the rate of fuel supply.
A control device implementing this principle is known for matching the fuel to the air, said device limiting the load on a diesel engine, in case the charging air is below normal pressure, incorporating an integrating device connected to a fuel supply sensor and to a charging air pressure sensor.
When the rate of fuel supply is properly matched with the rate of air supply (charging air pressure), the integrating device in which the ratio between the fuel and the air is programmed, forces down through an actuator a spring thrust limiting the displacement of a tailrod of the servo and disconnects the spring thrust in case charging air pressure exceeds the programmed value.
The mechanical action on the tailrod of the servo fails to provide its stable operation, which results in unstable fuel supply, while the loading of the mechanical linkage connecting the tailrod of the servo to a controlled element (fuel rod) causes an additional frictional wear on kinematic pair.
A fuel limiter designed by WOODWARD GOVERNOR CO for turbo-supercharged engines is also known. This fuel limiter adjusts the load on an engine as a function of charging air pressure.
The fuel limiter comprises a pressure sensor, charging air pressure being brought thereinto, and a kinematic linkage operatively connecting the pressure sensor with a cranckshaft speed measuring mechanism and with a tailrod of the servo, said kinematic linkage integrating the displacement of the pressure sensor actuator caused by changes in the rate of air supply and the displacement of the tailrod of the servo caused by changes in the rate of fuel supply and transmitting them to the pilot valve of the crankshaft speed measuring mechanism.
However, it is extremely difficult even for experienced governor technicians to adjust this type of control mechanism on an engine, therefore it is set on a test rig equipped with a means (e.g., a vacuum pump and manometer) capable of simulating different air pressures needed to check the linkage adjustments.
Also known is a diesel engine load limiting control device (Cf. U.S. Pat. No. 2,868,184), comprising a crankshaft speed measuring mechanism, a pilot valve mechanically connected to said crankshaft speed measuring mechanism, a sump containing hydraulic fluid, a pump located within said sump, a passage hydraulically connecting the pump to the pilot valve, a servomotor having a tailrod, a passage providing hydraulic linkage of the pilot valve with the servomotor, and a servomotor tailrod stroke limiter, said limiter having one movable element and being located within said passage providing hydraulic linkage of the pilot valve with the servomotor. The movable element of the servomotor tailrod stroke limiter is mechanically connected to the speed measuring mechanism, to the tailrod of the servomotor and to the pressure sensor, charging air pressure being brought thereinto.
The servomotor tailrod stroke limiter is connected to the sump through a passage.
Thus, the load control is provided as a function of rotational speed of the crankshaft of the diesel engine (rate of fuel supply) and of charging air pressure (rate of air supply) with the use of only one element, such a constructional arrangement resulting in an extremely intricate kinematic chain of the control device.
Besides, in the prior-art control devices the servomotor tailrod stroke limiter is arranged inside the control device and forms its integral part, thus preventing to employ said limiter as an independent unified assembly.